Most units within the AFFS, with the notable exception of the Ceti Hussars, are organized around a BattleMech regiment, which is roughly 108 'Mechs. To this regiment, conventional vehicles (tanks, V.T.O.L.s, etc.), artillery, infantry, and even aerospace fighters that complement the 'Mechs are traditionally attached. In some units, however, the AFFS took this a step further.

Many units within the AFFS are Regimental Combat Teams (RCTs). Front-line RCTs are composed of one 'Mech regiment, three of vehicles, a battalion of artillery, five regiments of infantry, and a fighter wing. Second-line, or militia, RCTs are usually composed of smaller numbers of these supporting forces. Front-line RCTs are usually commanded by a Marshal.